1. Proxy Pattern
Definition of “Proxy”: Authority or power to act for another
Original Gang of Four pattern, much used
Stands in for a “real object” (similar to a pointer)
Provides a public interface to the real object

2. Proxy Services Local interface Access control
Resource instantiation cost reduction

3. Types of Proxies
Protection Proxies grant or deny client access to the real subject (i.e., check permissions)
Remote Proxies are a local representation of a real subject in a different host (e.g., RMI)
Virtual Proxies represent expensive objects, such as images (e.g., replies to getHeight())
Smart Reference Proxies can count number of times referenced, act as lock or semaphore

4. Proxy UML Representation
Request ()
...()
Subject
Proxy
Client
RealSubject
realSubject
Abstract Class
Generalization
Aggregation
Interaction

5. Code Example private void init() { imgProxy = new ImageProxy (); }
//Do stuff to image
public ImageManipulation1() {
InitializeComponent();
init();
//Then instantiate image
private initiate(object, args) {
Real.Image = imgProxy.getImage ();